NOTE: Market shares are for the combined HMO+PPO product market.
* Data are from 2006 except for Miss. and Pa., which are from 2002-2003

Data: American Medical Assn., Competition in Health Insurance: A Comprehensive Study of U.S. Markets, 2008 update; James C. Robinson, "Consolidation and the Transformation of Competition in Health Insurance," Health Affairs, November/December 2004; Douglas McCarthy et al, "The North Dakota Experience: Achieving High-Performance Health Care Through Rural Innovation and Cooperation," The Commonwealth Fund, May 2008